package com.nulldev.util.VariableAPI.util.strings.splitters.third_party;

import java.util.Iterator;
import java.util.NoSuchElementException;

import com.nulldev.util.internal.codedapter.Nullable;
import static com.nulldev.util.data.Variables.checkState;

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
abstract class AbstractIterator<T> implements Iterator<T> {
	private State state = State.NOT_READY;

	protected AbstractIterator() {
	}

	private enum State {
		READY,
		NOT_READY,
		DONE,
		FAILED,
	}

	private @Nullable T next;

	protected abstract T computeNext();

	protected final @Nullable T endOfData() {
		state = State.DONE;
		return null;
	}

	@Override
	public final boolean hasNext() {
		checkState(state != State.FAILED);
		switch (state) {
			case DONE:
				return false;
			case READY:
				return true;
			default:
		}
		return tryToComputeNext();
	}

	private boolean tryToComputeNext() {
		state = State.FAILED; // temporary pessimism
		next = computeNext();
		if (state != State.DONE) {
			state = State.READY;
			return true;
		}
		return false;
	}

	@Override
	public final T next() {
		if (!hasNext()) {
			throw new NoSuchElementException();
		}
		state = State.NOT_READY;
		T result = next;
		next = null;
		return result;
	}

	@Override
	public final void remove() {
		throw new UnsupportedOperationException();
	}
}
